Question

Which of the following can be used to prove that triangle EFG is also a right triangle?

Prove that a + b is greater than c in triangle EFG so c2 = a2 + b2.
Prove that the sum of the squares of a and c in triangle EFG is greater than square of b in triangle KLM.
Prove that KL = EF so in triangle KLM a2 + b2 = c2.
Prove that KL = EF so in triangle KLM c2 = a2 + b2, which makes triangle EFG a right triangle.

Answer 1

Last option

Answer 2

If KL = EF, both triangles are identical , meanwhile, whenever you prove the c^2 = a^2 + b^2 for any of those , it's automatically proven for the other.